1. Technical Field
The present invention relates to a sample preparation apparatus and a sample preparation method as well as a cell analyzer and a cell analysis method.
Specifically, the present invention relates to the improvement of a preprocessing step including a cell concentration adjustment for preparing a measurement sample from a biological sample.
2. Background Art
Conventionally, as a cell analyzer for analyzing cells included in a biological sample extracted from a living body, there has been known a cell analyzer in which epidermal cells of a cervix included in a sample extracted from the cervix of a subject are measured by a flow cytometer to perform the screening of cancer cells and atypical cells (e.g., see the pamphlet of International Publication No. 2006/103920).
In the cell analyzer disclosed in the above pamphlet, a sample extracted from the cervix is mixed with various reagents to thereby prepare a measurement sample. Then, the prepared measurement sample is encompassed by sheath fluid and the sample is sent in a line in a sheath flow cell so that the cells in the measurement sample can be sent while being arranged in a line.
Then, the measurement sample is irradiated with laser beam. Then, the scattered light or fluorescence from the measurement sample is used to measure the size or shape of each cell.
However, some biological samples have remarkably-varied concentrations of measurement target cells. In the case of biological samples extracted from cervixes in particular, epidermal cells included in the respective samples have remarkably-varied concentrations.
The variation of concentrations as described above makes it difficult to accurately analyze the cells included in the biological samples.
For example, when a concentration of the measurement target cells in a biological sample is excessively low, the number of cells required to perform a significant analysis cannot be secured. Thus, it is difficult to detect cancer and atypical cells included in the measurement target cells. Furthermore, this also causes an increased influence of noise by cells other than the measurement target cells or dust for example. On the other hand, when the concentration of the measurement target cells in a living body is excessively high, it is difficult to detect all of the measurement target cells in the biological sample.
Furthermore, for example, in staining the measurement target cells by using a predetermined amount of staining fluid, when the concentration of the measurement target cells in the biological sample is excessively low, the measurement target cells may be excessively stained. On the other hand, when the concentration of the measurement target cells in the biological sample is excessively high, the measurement target cells may be insufficiently stained.